Universal bending mandrel utilizing connecting cable



2,825,386 UNIVERSAL BENDING MANDREL UTILIZING CONNECTING CABLE March 4, 1958 F. J. FUCHS, JR

2 Sheets-Shet 1 .Filed NOV- 17, 1954 INVENTOR FRANCIS J. FUCHS, Jr,

BY Q.. Q

ATTORNEY March 4, 1958 F. J. FUCHS, JR

UNIVERSAL BENDING MANDREL UTILIZING CONNECTING CABLE Filed Nov. .17, 1954 2 Sheets-Sheet 2 I v J z, W? x, 6 3 9 4 k Ely 1% w I w N Z INVENTOR P Q m UNIVERSAL BENDING MANDREL UTILIZING CONNECTING CABLE Francis J. Fuchs, In, Winston-Salem, N. C., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application November '17, 1954, Serial No. 469,471 3 Claims. Cl. 153-63 This invention relates to tube bending mandrels and more particularly to mandrels for supporting thin walled rectangular tubes during the bending of such tubes which are to be used as wave guides.

In the draw bending of wave guide tubing it has heretofore been proposed to utilize flexible mandrels whereby the inner surface of the tubing being bent is supported as uniformly as possible. These maudrels have comprised serially interconnected links which were interlinked by pin connections or ball and socket connections wherein each link was spaced from its next adjacent links by a fixed amount.

It is an object of the present invention to provide a mandrel of improved construction for use in bending rectangular wave guides. I

A further object of the invention is to provide a mandrel the componentsof which have a limited and adjustable amount of freedom of movement longitudinally of the mandrel. V

In accordance with one embodiment of the invention a plurality of mandrel elements having an outer contour conforming substantially to the inner contour of the tube to be bent and each having a semispherical projection at one side and a semispherical depression at the other side, are positioned side by side and held in engagement one with the otherby the upper and lower courses of flexible cable passing through apertures adjacent the ends of the mandrel elements and extending from a rigid stem through the upper ones of said apertures, through an arcuate passage in a terminal element, thence through the lower ones of said apertures in the mandrel elements and back to the stem. Preferably the stem comprises an assemblage, for attachment to the reciprocable mandrel rod of a draw bending machine, which has a cavity init for receiving the ends of the flexible cable together with a mechanism for adjustably'interconnecting'the ends of the cable whereby the length of the cable may be adjusted thereby to adjust the spacingof the mandrel elements.

In anotherembodiment of the invention the ends of the cable are 'adjustably attached directly to the stem bya plurality of set screws. e

A better understanding or the invention may be'had by reference to the accompahyiiig drawings wherein:

Fig; 1 is a srae ievafi snalview o'f'a 'r'ri andrel'ma'de in accordance with the present inventi ompartof the stem bes m w y; U. V v

Fig. 2 is a top view of the apparatus shown in Figure 1;

Fig. 3 is an enlar'ged'fragmentary side elevational view of a portion of 'the'rigid stem, parts being broken away to more clearly illustrate the constructional features;

Fig. 4 is a transverse sectional view taken along the line of Fig. 3 in the'direction of the arrows;

Fig. 5 is a transverse "sectional view taken along the line 5-5 in Fig. 3 in the direction of the arrows;

Fig. 6 is a view in perspective of a portion of the mechanism for adjustably interconnecting the ends of the cable;

ilnited States Patent 0 Fig. 7 is another perspective view showing another portion of said mechanism;

Fig. 8 is an enlarged fragmentary sectional view through the mandrel elements taken substantially along the "line 8--8 of Fig. 2 in the direction of the arrows;

Fig. 9 is a fragmentary sectional view taken along the line 99 of Fig. 8 in the direction of the arrows;

Fig. 10 is a fragmentary elevational view of the free end" of a stem illustrating an alternate embodiment of the'in-' vention, and

Fig. 11 is a transverse sectional view taken along the line 1111 of Fig. 10 in the direction of the arrows.

In accordance with the preferred embodiment 'of the invention there is provided a tube bending mandrel having a rigid stern designated generally by the numeral 15', an articulated body portion designated generally by the numeral 16 made up of a number of serially intercom-- nected links 17 and a terminal element designated generally by the numeral 18. The links 17, as seen most clearly in Figs. 8 and 9, have slightly rounded upper and lower ends 15 and 29 and are of a length substantially equal to the inside dimension of a section of wave guide which is to be bent using'the apparatus of the present inventiont' The sides 21 and 22 of the links 17 are also slightlyrounded and are spaced apart a distance substantially equal to the inside dimension across a section of wave guide which is to be bent by the present apparatus. Each of the links is provided with a semispherical depression:

upper and lower bell-mouthed apertures 28 and 29 respectively for receiving a flexible cable 30, the lower course of the cable extending through the aligned ape'rtures 29 and the upper course extending through the aligned apertures 28.

In addition to the links 17 having universal movement to a limited'extent one with respect to the other and with respect to the stem 15, there is also a limited amount of universal movement possible between the terminal ele-' ment 18 and the link 17 adjoiningit. The terminal ele ment 18 is composed of a pair of plates '33 and -34 suitably fastened together, for example by means of the rivets 35'.

38 which may be filled with solder in order to;strength the link 18. The plates 33 and 34 are provided with arcuate grooves 36 and 37 which cooperate when the plates are fixed together to form an arcuate passageway for the reception of a loop of the cable 30. The sides of the terminal element 18are rounded similarly'to the links 17 and the plates 33 and 34are tapered at their free end.

as shown at 40 (Fig. 9) to facilitate theinsertion of the mandrel into a wave guide to be bent. The outer edges of the plates 33 and 34 are rounded, as shown most clearly at 41 in Fig. 8, also to facilitate the insertion of the mandrel into a wave guide. I, e Therigid stem 15 is made from two substantially rectangular elongated bars 42 and 43 which when assembled are held together by machine screws 44. Bars 42,-and 43 are provided with a number of apertures throughw'hich dowels 45may be driven to align the assembled bars with Patented Mar. 4;-1-9ss The link 17 adjacent the stem 15 is formed in V The free ends of the plate 33 and 34--may, if desired, be beveled, whereby the assembled plates define a notch invention.

prises a mirror image of the plate 43.; Inaddition to the the plate as shown in Fig. 3.. Thisgroove 49 extends from the left end of the plates and then is curved through V a semicircular path as shown at 50 and thence is disposed tapered to merge with the'cavity 48. An e rtension of the groove 49 is resumed as'shown at 52 adjacent the left end of the rigid stem and this extension of the groove,

communicates with the cavityASa'djacent the left end of "the stem. The groove 49 "anditsfiextensions formed in each of the two plates 42' and '43 will, whenthe plates; 7 are attached together; forin a passageway-foithe recep- 1 tion of the lower and upper courses of the flexible cable'30.

The ends of the cable 30, prior tothetime when the plates 42 and 43 are assembled together, have blocks 60 and 61 -attached to them by means of -a'plurality of set screws 62'. The blocks '60 and 61,are slidable in tthc cavity 48 and are provided with longitudinally extending bores 63 and 64"the adjacent ends of which, when the blocks'are assembled'as shown in Fig. 3, areoppositely threaded as-shown at 65 and 66 for thereception of oppositely'thre'aded ends 67 and 68 of a shaft designated; generally by the numeral 69'. The mid portion of the' cavity 48, each of the plates is provided with agroove '49 extending adjacent tot'an'd parallel with the bottom edge of at a slight angle to the horizontal as shown at 51 and is 7 shaft-69 is slightly larger than the threaded portions and i is provided with teeth 70 for engagement by a suitable 1 tool'which maybe inserted through apertures 71in the plates 42' and 43,to rotate the shaft 69 thereby, to move the'blocks 60 and 61 toward or away from each other. I

In accordance with the embodiment of the invention I illustrated in Figs; '10 and 11, the articulated body portion of the mandrel is the same as in thepreviously, de-

" J scribed embodiment. However, the ends of the cable are simply attached to a rigidsternportion' designated generally by the numeral 75 byme'ans of a plurality "of v set screws 76. The set screws 76 are'threaded into aper- V tures'77 in a plate 78' which'is provided ,with' a" pair of grooves79 and 80 which are aligned with grooves 81and 82 in a cooperating plate 83. The plates 78 and 83 have I their right ends equipped in the's'ame manner as the right end of the rigid stem portion '15 in the preferred embodiment of the invention and havea semispherical depression84 at their left end, Fig. 10. H In'using the apparatus'of the preferred embodiment of the invention,.the spacingof the links'17 longitudinally of the mandrel may be adjusted by rotating the shaft 69 :which will eithershorten'or lengthen the cable 30; and, V consequently, will adjust the pressure between thedepres -sions 25; and 27 and projections'26 on' the various links 17 whereby when it is desired to extendxor shorten the articulated portion of the mandrel slightly the cable'may be lengthened by rotating the shaft 69in one direction and may be shortened by rotatingthe shaft 69 in the opposite direction; The adjustment of thelength of the cable embodiment illustrated in Figs; '10 and 11 may be I effected ,by loosening either the upper or lower set screws 76 and resetting them in the desired positions r Although specific embodiments ofthe invention have been described herein it will be understood that modificatio'nsflthereof maybe inade'without departing from the 'What is claimed is: 1

; l. Atube bendingmandrel comprising a rigid stem,

a plurality of body links thefouter contour of which con I forms substantially to' the interior contour of a .tube tobe bent, abutting surfaces of said links and said stem being formed to permit movement of each link with respect to 1 itsadjoining links and of the inner endrlink with respect dividually" to said' blocks. ,2. A tube ibending mandrel ing the links one to the other and'to the stem comprising having teeth "at its 'mid portion and oppositely threaded ends threaded into said bores, cooperating groovesjin the abuttingzfaces of said bars forming a U-shaped' guide passagefor, said cable, and means for fixing the ends of said cablein opposite'endsof said'blocks. 7 a

3. A' tube bending mandrel comprising arigidT'stem,-: V a plurality of body-links the outer-contour ofwhich Icon-i 7 forms substantially to the'interi'or'contourof -a tube 't'o'be a i bent, abutting surfaces of saidlinks and said'stem being formed topermit universial'movement-of each link with;

respectto its adjoining links and of the inner'end link V "with respect to the "stem-and means for attaching thex links one to the other and to-the stem comprising a flex-- ible cable threaded through said links iandhaving'its ends adjustably attached to said stein, said stern having a cavity f V a -.in it, a pair'of :blocks 'slidably mounted in said cavity, a means for attachingthe ends of thecable individuallyt'o a said blocks, and meansfor adjusting the 'blocks'withre- 1 spect one to another thereby to vary the effective length I V of said cable] 1 r 1 1 1 i Ref ei'ences Cited the 'file'of thispatent, we

V comprising a rigid stem atplurality of bodytlinks the outer contour of which con-' forms substantiallyto the interior contour of a tube to be bent, abutting surfaces 'ofsaidlinks and said stem' being; 5 formed to permit limited universal movement of each link with'respect to its adjoining links ande of the inner endlinkwith respect to the stem, and meansforatt'ach y May 17, 1954,; 

